Rotating electric machines are used for a wide variety of applications, such as automotive applications, aerospace applications, industrial applications, and/or the like. Rotating electric machines include a rotor and a stator. A rotating electric machine may be an electrical motor, wherein the rotor rotates relative to the stator to convert electrical energy to mechanical energy. Rotating electric machines also include electrical generators, wherein the relative rotation between the rotor and the stator converts mechanical energy to electrical energy.
The stators of some rotating electric machines include a stator core having coils that are wound around stator teeth of the stator core. The coils are wound around the stator teeth within stator slots that separate the stator teeth. Slot liners may be provided within the stator slots to electrically isolate the coils from the stator core. In addition or alternatively, slot liners may be provided within rotor slots of the rotor of the electric machine to electrically isolate rotor coils from the rotor core. But, known slot liners are not without disadvantages. For example, some known slot liners consist of a neat polyimide (e.g., Kapton®) film, which has a relatively low thermal conductivity. Such a relatively low thermal conductivity may be a barrier to increasing the power density of some rotating electric machines, for example aircraft starter generators.
It is known to increase the thermal conductivity of neat polyimide films by adding a filler material. But, the amount of filler material necessary to increase the thermal conductivity of the neat polyimide film to a level that enables an increase in power density may increase the brittleness of the neat polyimide film. The increased brittleness of the neat polyimide film of the slot liner may cause the neat polyimide film to tear, fracture, and/or otherwise break as the windings of the coil are wound around the stator or rotor teeth, which may result in failure of the slot liner to electrically isolate the coil from the stator or rotor core.